Effec to fLive rResectio no nth eProgressio nan dGrowt hof Rhabdomyosarcom aMetastase si na Ra tModel

Background/Aims. To analyze the effect of liver resection on the progression of liver metastases in a rhabdomyosarcoma rat model. Methods. Liver metastases were induced by intrasplenic injection of S4MH rhabdomyosarcoma cells in WAG/RijCrl rats. In a first experiment, rats were sequentially sacrificed until day 30 following tumor cell inoculation to establish the optimal day to evaluate liver and lung metastases. A second group of rats were hepatectomized or laparotomized 10 d after tumor inoculation, and on day 21 they were sacrificed to determine the size and number of liver and lung metastases. Also, in vitro proliferation rates of tumor cells in the presence of fetal calf serum or hepatectomized or laparotomized rat serum were assessed. Results. Individual metastases could be optimally determined on day 21. In hepatectomized animals liver metastases reached greater size and their number was significantly increased (28.7 versus 9.3, P < 0.05). Moreover, the number of lung tumor foci in this group nearly doubled that in the control group (99.2 versus 28.5, P < 0.05). In vitro studies showed that hepatectomized rat serum increased cell proliferation when compared with laparotomized rat serum (2.0fold) or fetal calf serum (1.4-fold). Conclusions. This tumor model shows the tumorenhancing effect derived from hepatic resection, and may be useful to assess preventive therapeutic